Composite alloy



Nov. 17, 1953 T. E. LEONTIS ET AL COMPOSITE ALLOY Filed Aug. '16, 1950INVENTORS. Thomas E. Leon/11$ BY Rober/ S. Busk AZMZ A ITORNE rsPatented Nov. 17, 1953 COIVIPOSITE ALLOY Thomas E. Leontis and Robert S.Busk, Midland,

Mich., assignors to The Dow Chemical Company, Midland, Mich., acorporation of Delaware Application August 16, 1950, Serial N o. 179,776

7 Claims.

The invention relates to a composite metal body of which magnesium isthe predominant constituent. t more particularly concerns an improvedmagnesium-base alloy product containing magnesium with which aluminum isal loyed.

The term magnesium-base alloy used herein means a magnesium alloycontaining at least 80 per cent of magnesium by weight.

The common magnesium-base alloys used for structural purposes owe theirstrength at least in part to the aluminum with which they are alloyed.In addition to aluminum, these alloys usually also contain either orboth zinc and manganese and sometimes also calcium. Although thealuminum-containing magnesiumbase alloys are among the strongest of themagnesium-base alloys, nevertheless there is an ever present desideratumin the art to provide still stronger magnesium-base alloys.

According to the present invention, composite magnesium-base alloyscontaining aluminum are formed by extruding an aluminum-containingmagnesium-base alloy in particulated form in admixture with anadditional amount of particulated aluminum. The mixture of particulatedmetals thus extruded may also contain other particulatedmagnesium-soluble metals, such as silver, cerium, manganese, lead, tin,and zinc in amount up to l per cent by weight. The extrusionobtained isa composite alloy having the same compactness and integrity as the usualmagnesium-base alloy extrusions made by extruding a solid mass, such asan ingot of a magnesium-base alloy and can be worked, as by rolling,forging, pressing, drawing, etc., like conventional magnesium-basealloys, but the metallographic structure of the composite alloy isuniquely different. Metallographic examination reveals a new type ofstructure in a magnesium-base alloy article. The structure isessentially multimetallic. Each of the two particulate metals of themixture which is extruded is changed to the form of elongated fineparticles with the long axis parallel to that of the extrusion and theseelongated particles are interspersed and welded one to the other withoutvoids forming a solid composite mass. There is diffusion of some of theparticulated aluminum ingredient into the particulated aluminum-con;-taining magnesium-base alloy; and there is some diiiusion of magnesiumfrom the particulated aluminum-containing magnesium-base alloy into theparticulated aluminum. When manganese is present in the particulatedaluminum-containing magnesium-base alloy more or less may beprecipitated by the diffused aluminum. The composite alloy obtained maybe subjected to the same types of metal working operations as employedwith conventional magnesium-base alloys, e. g. rolling, welding,forging, heat treatment, chemical finishing, electroplating, etc. Themechanical properties of the composite alloy generally surpass those ofthe conventional alumihum-containing magnesium-base alloy. A particularadvantage of the composite alloy is its ability to resist loss ofstrength when worked in heated condition.

In carrying out the invention, the aluminum content of thealuminum-containing magnesiumbase alloy is not sharply critical. Amountsas low as 0.1 per cent and as high as 12 per cent may be used. Generallydesirable results are had with from about 3 to 6 per cent of aluminumparticularly when the alloy also contains zinc. The amount of zinc, ifpresent in the aluminum-containing magnesium-base alloy, may be fromabout 0.5 to 3 per cent. If desired, manganese in conventional amount,e. g. 0.1 to 2 per cent also may be present in the aluminum-containingmagnesium-base alloy, the amount actually used being subject to itssolubility limit in magnesium containing alloyed aluminum as understoodin the art; also up to 0.5 per cent of calcium may be present.

The aluminum-containing magnesium-base alloy used as one of theingredients of the composite alloy of the invention is reduced toparticulate form in any suitable way, such as by grinding or atomizing.The atomized form is preferred and may be produced by forming a melt ofthe alloy and atomizing it by impinging a jet of a cool gas, e. g.natural gas, against a thin falling stream of the molten alloy. Theatomized alloy consists of a mixture of various sized fine sphericalrapidly solidified particles, the particles having a very fine grainstructure. It is desirable to screen out particles coarser than thosepassing about a 10 to 20 mesh sieve.

The aluminum ingredient of the mixture of particulate metals to beextruded according to the invention, is elementary aluminum which hasbeen finely divided in any convenient manner. Its particle size ispreferably made finer than that of the aluminum-containingmagnesium-base alloy with which it is to be mixed.

Before extrusion, the metals in particulate form are mixed together inany convenient mand ner to form a uniform mixture of the metal particlescomprising the extrusion charge. The relative amounts of theparticulated aluminumcontaining magnesium-base alloy and theparticulated aluminum are adjusted so that there is in the mixture atleast .1% by weight of particulated aluminum. Beneficial results are hadwith up to as much as about 6% of particulated aluminum in the mixture.A preferred propor tion is about 3% of the particulated aluminum in themixture.

The mixture of particulate metals is charged into the heated containerof a ram extruder, having a suitable size container and die opening andsubjected to extrusion pressure to cause the mixture of particulatemetals to be heated and extruded through the die opening,

As to the extrusion conditions, the temperature of the particulatedmixture in the container may be about the same as thatconventional-131cm ployed for extruding solid ingots of the knownaluminum-containing magnesium-base alloys, e. g. from about 650 toSki-07F. The ratio of the cross-sectional area of the extrusioncontainer to that of the die opening has amaterial effect on ,themechanical properties of the composite extrusion product obtained. Adesirable ratio is at. least about SO to 1, although ratios as high as150 to, 1 or more may be used. The speed of extrusion maybe varied overawide range and depends to someextent upon the size and shape of the dieopening, in any case the speed is tobe helddown to that at which theextrusion produced is free from hot shortness. A safe extrusion speedmay be ascertained by visual examination of the product as it extrudes,the hot shortness being evident as cracksin the extruded product andsharply reduced strength.

The invention may be further illustrated and explained in connectionwith the accompanying drawing in which:

Fig. 1 shows a schematic sectional elevation of an extrusion apparatussuitable for use in practicing the invention;

Fig. 2 isa, similar view to Fig. 1 showing a modiis provided with aheating element 3. In Fig. 1 one end of the container 1 is closed by thedie plate 4 in which is provided the die opening. In this form of theapparatus, the charge 2 is caused to be compacted in the container andextruded through the die opening 5 by application of pressure by meansof the dummy block 6 forced into the bore 1 of the gcontainerby the ram8 to form the composite alloy extrusion 9.

In the form of the apparatus shown in Fig. 2, the container 1 is closedat one end by the plate I0. The other end of the container receives thedie block ll carried by the hollow ram l2 which forces the die blockinto the container causing the charge 2 to'be compacted and to extrudethrough dieopening l3 to form the composite alloy extrusion 14 whichextends into bore H) of the hollow ram 12.

In the modification of Fig. 3, the container l is closed at one end by aplate H5. The charge 2 is extruded as a tubular "composite alloyextrusion ll through the annulus [8 around the die block 19 while theblock is forced into the container .by the ram 20. H a

The forms of the apparatus shown are conventional. I 7

By putting a charge of the mixture of the two particulate metalsinvolved under pressure while at heat, as with the apparatus shown, the'rhixture of metal particles-is compacted but not sub; jected to furthermixing before extrusion. The metals in the charge as individualparticle's become welded together without voids and substantiallywithout losing their original distinctive composition except at thesurfaces of the union of the different ,kinds of particles which becomeextended and lengthened during extrusion; At these surfaces,someintermixingoccurs, as by diffusion, between the particles of thedifferent metals in the extrusionc'ha'rge, forming composite alloy. Inthis difiusidn, some 'of the aluminum ingredient of the aluminumparticles diffuses into the aluminum-containing magnesium alloyparticles and some of themagnesium of the aluminum containi'nigmagnesium alloy particles ficat1on of the apparatus; and d ffuses mtothe alummun particles. In addi- F 3 Ba Similar View to 1 Showing ationysome precipitation of manganese may be inother modification of tppa atus. duced whencontained in the aluminum contain- As shown, theapparatus comprises, inits three ing magnesium alloy particles. v forms,an extrusion container l adapted to con- 50 The following series ofexamples set forth in fine. a charge 2 ofthe mixture of the particlesthe table herewith are illustrative of the invenof the metals to becoextruded. The container tio Table Composition of extrusion charge ofparticulated Extrusion conditions Mechanical properties in LOIlOs p. s.i. of extrusions y l A mixed with particulated aluminum Exlample Asx A 1H T H r A ge Blank N0.. Weight 1 y 1 7 Weight Temp., figg g' percentAnalysis of A percent F, h 1 v V A r A area TYS Ts 'IYS TS TYS 'rs TYSTe -0. 5 670 34:1 0. 086. .30 ,44 3o 44 .41 26 .39 6. 0 650 34:1 0. 08632 43 31 43 26' 3s 27 34 1. 0 700 34:1 0. 086 30 43 31 43 2s 41 i 29 42None 100 34:1 0. 086 28 42 3o 44 26 41 I 26 42 o. 1 v 665 34:1 0. 086,39 4s 37 47 27 41 26 42 0. 5' 665' 34:1 '0. use 3s .45 3s 45 .24 ,39 23.30 6.0 665 34:1 0. 086. 40 3s 41 29 37 52 37 one 700 341' 0. 086' 40 4740 47 24 3s 25 is 1. 0 100 34:1 0.086 .40 47 4o 47 31 40 31 39 None 70034:1 0.086 39 46 33 461 27 .39 .25 39 1 2 670 34:1 0.086 39 46 .38. 45'v29. 42 31 2 2 670- 34:1 0.086 38 46 3s 46 30' 41 30 42 3 2 670 34:10.086 as 45 39 4s .29 .42 31 42 4 2 e70 34:1 0. 086 37 45 3s .44 2s .43z]. 42 4 2 670 34:1 0. use 3s 46 as 45 23 42 28 41 B 2 670 34: 1 0. 08639 48' 3s '45 2s. 41 30. 4o 4 I 5% Zn, 05% 0:1 740 30:1 0.092 45 491 46;50 4o 46 4o 46 A. Mn, 0.09% Qa, bal. Mg. k -.d0 '0.5 *740 3051 o. 192 4550 -47 41. 40' '47 J42 4 Composition of extrusion charge of particulatedExtrusion conditions Mechanical properties in 1,000s p. s. i. ofextrusions A mixed with particulated aluminum Elxramplc S d H A A X Age.'1. H. I.- Blank No, W eight Weight Temp., figg g' percent Analysis ofA percent F. area inch A A1 TYS TS TYS TS TYS TS 'IYS TS 16 99. 0 0.25%Al, 0.55% Zn, 0.05% 1.0 740 :1 0. 092 46 50 41 48 42 48 Mn, 0.09% Ga,bal. Mg. 17 97. 0 do 3. 0 740 30:1 0. 092 45 49 46 49 41 47 43 49 18 94.0 -do 6.0 740 30:1 0. 092 44 46 47 47 45 49 46 47 Blank 4.. 100 .do None740 30:1 0. 092 43 48 45 48 38 45 38 44 1 1% Al-HV, Ag. 2 1% Al+l% Ge.1% Al+1% Mn.

5 1% Al+1% n.

*A$X=as extruded.

A ed =heated 16 hours at 350 F. H. T.=heated 1 hour at 750 F.

H. T. A.=beated 1 hour at 750 F. followed b heating for 16 hours at 350F. 'IYS =Tensi1e yield strength defined as the stress at which thestress strain curve deviates 0.2% from the modulus line.

TS =tensile strength.

In making the composite alloys and blanks for comparison, set forth inthe said table, the particulated aluminum-containing magnesium-basealloy and the particulated elementary aluminum used comprised particlesof various sizes substantially all passing a No. 20 standard sieve,although the particulated elementary aluminum was generally finer thanthe particulated magnesiumbase alloy. The two particulated metals weremixed together in the proportions indicated and the mixture charged intothe heated container of a ram extruder of the type illustrated inFig. 1. For the blanks, individual particulated metals were extruded insimilar manner. The rate of extrusion did not exceed about 5 feet perminute. It will be seen by referring to the table that in Examples 1, 2and 3 the particulated magnesiumbase alloy used to make the compositealloy contained aluminum; in Examples 4, 5, 6 and 7 the particulatedmagnesium-base alloy contained aluminum, zinc, and manganese; inExamples 8 to 13, inclusive, the same magnesium-base alloy was used asthat in Example 7 together with 1 per cent of each of two particulatedelementary (unalloyed) metals, including aluminum, as shown by thefootnotes to 6, inclusive. In Examples 14 to 18, inclusive, theparticulated magnesium-base alloy contained zinc, in addition toaluminum, manganese, and calcium.

Among the advantages of the invention are that the metal productobtained has the characteristic lightness of conventional magnesiumbasealloys but with increased strength.

We claim:

1. The method of making a solid composite article comprising analuminum-containing magnesium-base alloy which comprises forming amixture consisting of up to 1 per cent by weight of a particulatedmagnesium-soluble metal selected from the group consisting of silver,cerium, manganese, lead, tin, and zinc, from 0.1 to 12 per cent ofparticulated aluminum, the balance of the mixture being a particulatedmagnesiumbase alloy containing 0.1 to 12 per cent of aluminum, up to 3per cent of zinc, up to 2 per cent of manganese, and up to 0.5 per centof calcium, the balance of the alloy being magnesium, and die-expressingthe mixture at a temperature between about 650 and 850 F.

2. The method according to claim 1 in which the particulatedmagnesium-base alloy containing from 0.1 to 12 per cent of aluminum,also contains 0.5 to 3 per cent of zinc.

3. The method according to claim 1 in which the particulatedmagnesium-base alloy containing from 0.1 to 12 per cent of aluminum,also contains 0.5 to 3 per cent of zinc, and 0.1 to 2 per cent ofmanganese.

4. The method according to claim 1 follovt ed by subjecting thedie-expressed article to a prolonged heating at about 350 F.

5. The method according to claim 1 followed by subjecting thedie-expressed article to a prolonged heating at about 750 F.

6. The method according to claim 5 followed by subjecting the heateddie-expressed article to a further prolonged heating at about 350 F.

7. A composite metal body consisting of a plurality of metals inparticulate form one of the metals being a magnesium-soluble metalselected from the group consisting of silver, cerium, manganese, lead,tin, and zinc in amount up to 1 per cent of the weight of the body,another of the metals being aluminum in amount between 0.1 and 12 percent, and the balance of the metals being a magnesium-base alloycontaining 0.1 to 12 per cent of aluminum, up to 3 per cent of zinc, upto 2 per cent of manganese, up to 0.5 per cent of calcium, the balanceof the magnesium-base alloy being magnesium, the particles of each ofthe said metals being elongated, orientated in the same direction, andall welded together into an integral solid.

THOMAS E. LEONTIS. ROBERT S. BUSK.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,913,133 Stout June 6, 1933 2,024,767 Jefiries et al. Dec.17, 1935 2,205,865 Schwarzkofi June 25, 1940 2,332,277 Stern Oct. 29,1943 2,355,954 Cremer Aug. 15, 1944 FOREIGN PATENTS Number Country Date570,166 Great Britain June 26, 1945 570,906 Great Britain July 27, 1945625,364 Great Britain June 27, 1949 OTHER REFERENCES Treatise on PowderMetallurgy by Goetzel, vol. 2, pp. 500,740, 741. Published in 1950.

Symposium on Powder Metallurgy, Buifalo Spring Meeting, March 3, 1943,published by American Society for Testing Materials, Philadelphia, Pa,pages 42 and 43.

7. A COMPOSITE METAL BODY CONSISTING OF A PLURALITY OF METALS INPARTICULATE FORM ONE OF THE METALS BEING A MAGNESIUM-SOLUBLE METALSELECTED FROM THE GROUP CONSISTING OF SILVER, CERIUM, MANGANESE, LEAD,TIN, AND ZINC IN AMOUNT UP TO 1 PER CENT OF THE WEIGHT OF THE BODY,ANOTHER OF THE METALS BEING ALUMINUM IN AMOUNT BETWEEN 0.1 AND 12 PERCENT, AND THE BALANCE OF THE METALS BEING A MAGNESIUM-BASE ALLOYCONTAINING 0.1 TO 12 PER CNET OF ALUMINUM, UP TO 3 PER CENT ZINC, UP TO2 PER CENT OF MANGANESE, UP TO 0.5 PER CENT OF CALCIUM, THE BALANCE OFTHE MAGNESIUM-BASE ALLOY BEING MAGNESIUM, THE PARTICLES OF EACH OF THESAID METALS BEING ELONGATED, ORIENTATED IN THE SAME DIRECTION, AND ALLWELDED TOGETHER INTO AN INTEGRAL SOLID.